Workaround doom-modeline issues

[thiagokokada]

• Some clean-ups backported from Bump doom-emacs #316.
• Remove doom-modeline pin and re-added missing functions as suggested in Symbol’s function definition is void: doom-modeline-set-vcs-modeline #309 (comment). The reason for this is because trying to keep track of doom-modeline and the changes in other packages will mean that we will eventually need to pin many packages to its own working version (see +doom-dashboard-init-h (void-function doom-modeline-set-project-modeline) #325), while just restoring the missing functions will mean that we (theoretically) can just use the most up-to-date version of doom-modeline instead. At least until doom-modeline does another breaking change, that is

[thiagokokada]

This PR seems to have the unintended side-effect of also fixing doom-modeline in Emacs stable.

[thiagokokada]

CC @ckiee for review, seems to fix the issue from #326.

[ckiee]

Tests build, dashboard only works on Emacs 29 but that isn't new I think. Very nice work (: